I just learned that my boss's adult son keeps a choke chain collar on their Mexican hairless terrier dog (don't know actual breed name, its a medium sized black hairless dog). They treat the dog really well but are just ignorant on this issue. The dog stays in the house alone when they are out so I'm afraid he will catch the ring on something and choke himself. I need a good reference page from a reputable source (that a novice dog person might know of) that I can print out and give them regarding the danger of leaving a chain choke collar on your dog unattended. They have always thought its just a regular collar like a nylon collar and have not thought of it as purely a training collar. Any suggestions for a good reference? I've googled it but haven't found anything.